It basically depends on what type of horror you prefer. If it's supernatural then Paranormal Activities are the kings and queens and um The Ring II
But if you prefer bloodshed stuff then I've got somethings in my bag
Hostel
Saw
The Hills Have Eyes
Friday the 13th
1408
I Know What You Did Last Summer
Sixth Sense (it was alright)
I don't have the best of them, but these are the ones I highly recommend.